Posted the comparison of new M3 vs CSL in other thread but some people are curious about how old (E46) M3 stacks up against its lightweight version.

http://www.youtube.com/watch?v=QhPSS9fGvwM

Difference of better tires, quicker steering, a lot lighter weight and little bit more power with somewhat better brakes do in 1.1 mile long track. The gap increases to ridiculous 10 secs or so on 14 miles long Nordschleife.